火灾下三面和两相邻面受火H形截面钢柱的临界温度

Critical Temperature of H-section Steel Columns Heated from Three or Two Adjacent Sides

三面受火钢柱可能发生绕强轴的弯曲失稳或绕弱轴的弯扭失稳,而两相邻面受火钢柱仅发生弯扭失稳。将钢柱截面温度场假设成简化的线性分布,对不均匀受火钢柱进行恒荷载升温分析,可得到钢柱发生整体失稳破坏时的临界温度。三面受火钢柱的临界温度与欧洲规范EN 1993-1-2的结果较为接近,可直接由EN 1993-1-2公式计算。对于两相邻面受火钢柱,可由EN 1993-1-2的计算结果乘以修正系数,文中给出了该修正系数的计算公式。

Temperature gradient occurs when a steel column is heated non-uniformly in a fire.For three-side heated column,thermal gradient exists along the depth of H-section.But for the column exposed to the fire from two adjacent sides,thermal gradient exists both along the width and depth of H-section.In this paper,the critical temperature of steel columns exposed to fire from three sides and two adjacent sides is obtained through a structural analysis model.Temperature profile across the section is assumed as linear distributions.The three-side heated steel column may fail due to flexural buckling or flexural-torsional buckling.And the column exposed to fire from two adjacent sides may fail due to flexural-torsional buckling.EN1993-1-2 could provide a slightly conservative estimate of the critical temperature of three-side heated steel column.But for the two-side heated column,a correction factor is proposed to modify the calculation results of EN1993-1-2.The equation for calculating this correction factor with respect to different slenderness ratio and load ratio is provided.